Regulation of surface synthesis in Streptococcus mutans GS-5 will be examined in three systems. In the first system we will look at the regulation of the expression of two cloned genes, gtfB and gtfC. We will use for this purpose a series of apparent deletion mutants that express varying amounts of antigen-reactive and enzymatically active glucosyltransferase. The mutants will be characterized biochemically and by restriction mapping in an effort to pinpoint various regulatory regions. The putative promoter of gtfB will be cloned in a promoter vector and examined for possible effects of sucrose on expression of these gtf genes in S. mutans. We will study serotype c polysaccharide biosynthesis using 4 mutants that were obtained using MAbs generated against different epitopes. We will complement the genetic defects with DNA cloned into a streptococcal vector. In a third series of experiments, we will identify, and characterize surface-associated and supernate proteins produced by S. mutans GS-5 under various growth conditions and will identify and/or generate monoclonal antibodies (MAbs) to these proteins. The MAbs will then be used to isolate and identify Tn9l7-inactivated mutants of S. mutans for various surface proteins. The use of Tn9l7 inactivation will permit mapping of the mutation, rapid cloning of a portion of the inactivated gene, and eventually, molecular characterization.